1. Field of the Invention
The invention relates to a method of producing a dielectric layer and somewhat more particularly to a method of producing a dielectric layer useful as a glow or a light-modulating element or display device which utilize an electro-optical effect or surface wave transmission medium.
2. Prior Art
The prior art has suggested using dielectric layers having an electro-optical effect and composed of crystalline materials, such as, for example, bismuth-silicon oxide or bismuth-germanium oxide. Such dielectric layers may be produced by the crystal pulling techniques and formed so as to have a sufficiently large area for use in electro-optical devices. However, these prior art dielectric layers exhibit a large electrical conductivity when irradiated by light or a large photoconductive effect so that the application of an electrical field onto such dielectric layer is disturbed. Further, these prior art dielectric layers have a large absorption of visible light so that optical signals transmitted therethrough may be distorted.
An electro-optical crystalline material which is low in photoconductivity and low in absorption of visible light is disclosed in Japanese Patent Application No. 29931/74 (Laid-Open Document No. 130466/1975). However, it is extremely difficult or impossible to produce such crystalline materials, which comprise bismuth-germanium oxide or bismuth-silicon oxide doped with Ga and an element selected from the group consisting of Ba, Ca, Mg and Sr with a sufficiently large area for use in electro-optical devices.